The present invention relates to radiotherapy and, more particularly, to a method and device for radiotherapy using decay chain nuclei of a radionuclide.
Cancer is a major cause of death in the modem world. Effective treatment of cancer is most readily accomplished following early detection of malignant tumors. Most techniques used to treat cancer (other than chemotherapy) are directed against a defined tumor site in an organ, such as brain, breast, ovary, colon and the like.
When a mass of abnormal cells is consolidated and is sufficiently large, surgical removal, destruction of the tumor mass using heating, cooling, irradiative or chemical ablation becomes possible because the target is readily identifiable and localizable. However, it is not uncommon for a cancer that has initially occurred at a primary site to metastasize and spread into adjacent organs as diffuse clusters of abnormal cells.
Known in the art are several procedures for treating tumors by irradiation. One such procedure employs laser light, which can destruct unwanted cells either through a direct interaction between the laser beam and the tissue, or through activation of some photochemical reactions using light-activated molecules which are injected into or otherwise administered to the tissue. For example, in a procedure, known as Photo-dynamic therapy (PDT), a photosensitive drug that binds to rapidly dividing cells is administered to the subject. Subsequently, the photosensitive drug is irradiated using a narrow-band laser so as to induce a chemical reaction resulting in a production of reactive products which then destroy the abnormal tissue.
The PDT technique suffers from a number of drawbacks and limitations. It is necessary to deliver a large amount of light radiation to the tumor at specific wavelengths to activate the photosensitive agent. Most photosensitive agents are activated at wavelengths that can only penetrate through three or less centimeters of tissue. Hence, non- or minimal-invasive PDT can be used for cancerous growths that are on or near the surface of the skin, or on the lining of internal organs.
Radiation therapy, also referred to as radiotherapy, or therapeutic radiology, is the use of radiation sources in the treatment or relief of diseases. Radiotherapy typically makes use of ionizing radiation, deep tissue-penetrating rays, which can physically and chemically react with diseased cells to destroy them. Each therapy program has a radiation dosage defined by the type and amount of radiation for each treatment session, frequency of treatment session and total of number of sessions.
Radiotherapy is particularly suitable for treating solid tumors, which have a well-defined spatial contour. Such tumors are encountered in breast, kidney and prostate cancer, as well as in secondary growths in the brain, lungs and liver.
Conventionally, the mainstream of the radiotherapy is toward the so-called treatment through external irradiation, that is, treating an internal tumor grown in a human subject with a radiation of an external source (e.g., of gamma rays). Alternatively, a radioactive source (typically an electron emitting source) is inserted into the body.
To avoid adversely affecting any healthy region of the subject, one attempts to maximize the dose administered to the target zone (to ensure killing the cancerous cells) while minimizing the dose to other regions (to avoid undesirable damage). Most commonly, radiotherapy is used as an adjunct way of use, such as treating those remnant, not entirely removed, tumor cells by being exposed to a radiation dose of an external source after the surgical opening of the human body, removal of malignant tumors and the suture of the body parts or radiating the radiation dose directly to the remnant tumor cells before the suture of the body parts involved.
It is well known that different types of radiation differ widely in their cell killing efficiency. Gamma and beta rays have a relatively low efficiency. By contrast, alpha particles as well as other heavy charged particles are capable of transferring larger amount of energies, hence being extremely efficient. In certain conditions, the energy transferred by a single heavy particle is sufficient to destroy a cell. Moreover, the non-specific irradiation of normal tissue around the target cell is greatly reduced or absent because heavy particles can deliver the radiation over the distance of a few cells diameters.
On the other hand, the fact that their range in human tissue is less than 0.1 millimeter, limits the number of procedures in which heavy particles can be used. More specifically, conventional radiotherapy by alpha particles is typically performed externally when the tumor is on the surface of the skin.
There is thus a widely recognized need for, and it would be highly advantageous to have a method and device for radiotherapy using alpha particles and decay chain nuclei of a radionuclide, devoid of the above limitations.